This application is based on and claims priority to Japanese Patent Application No. 2000-215160, filed Jul. 14, 2000, the entire contents of which are hereby expressly incorporated by reference.
1. Field of the Invention
The present invention generally relates to a ventilation arrangement for an outboard motor, and more particularly relates to a cowling air inlet arrangement for an outboard motor.
2. Description of the Related Art
Outboard motors are often powered by internal combustion engines. The engine is typically positioned within a substantially enclosed cowling. The engine is generally vertically arranged, so that a crankshaft thereof may extend downwardly in driving relation with a water propulsion device of the motor, such as a propeller. In order to balance the motor, and because of space considerations, the engine is arranged with a crankcase of the engine facing in the direction of a watercraft to which the motor is mounted (i.e., positioned on a front side of the engine) and with the cylinder head positioned on an end of the engine facing away from the watercraft (i.e., positioned on a rear side of the engine).
Four-cycle internal combustion engines tend to have advantageous emission control and high performance relative to two-cycle internal combustion engines. Accordingly, it is becoming popular for outboard motors to employ such four-cycle internal combustion engines. Typically, the four-cycle engine has intake and exhaust ports, both of which communicate with a combustion chamber. Typical engine arrangements usually position the intake ports along a side of the engine. Intake pipes supply intake air to the intake ports and extend along the side of the engine. Throttle bodies are usually positioned along the intake pipes. The intake ports and the intake pipes form at least a portion of an induction system.
Air must be supplied to the engine through the cowling for combustion. The cowling is sometimes divided into an engine compartment and an air guide chamber, with an air vent in the cowling communicating with the air guide chamber. Outside air is supplied to the engine through the air vent and the air guide chamber. Thus, ambient air is drawn through the air vent and the enclosed air guide chamber to the induction system. In order to inhibit the direct entry of water through the air vent into the intake system, the air vent generally is positioned away from the intake system, typically in the end of the engine facing away from the watercraft.
Certain four-cycle engine components, such as the throttle bodies, that are typically positioned on the side of the engine, are especially sensitive to corrosion that may occur when water enters the cowling through the intake duct and splashes onto the component. For example, corrosion may damage a rotating throttle valve shaft, thus disrupting smooth operation of the throttles. Additionally, when used in a marine environment, water contacting the moving components (i.e., throttle valve shafts) can leave mineral deposits that can hamper proper movement.
A need therefore exists for an improved water preclusion arrangement for an outboard motor, which arrangement will protect vulnerable engine components from contact with water and will also reduce water ingestion by the engine.
In accordance with one aspect, the present ventilation arrangement includes an outboard motor comprising a cowling substantially enclosing an internal combustion engine. The engine comprises an air intake system and an engine cover. The intake system has an intake opening disposed near a front end of the engine. The engine cover is disposed above an upper end of the engine. The cowling has an air inlet formed through an upper rear end of the cowling. An air guide member comprises a base plate disposed between the air inlet and the engine cover. The base plate has an air duct extending therethrough. The air duct is offset from a longitudinal center line of the engine and opens above the engine cover. A transverse base plate rib extends downward from the base plate at a location forward of the air duct. A pair of longitudinal base plate ribs extend downward from the base plate and are connected to the transverse base plate rib such that the air duct is interposed therebetween. A transverse cover rib extends upward from the cover proximate the transverse base plate rib. A pair of longitudinal cover ribs extend upward from the cover proximate the longitudinal base plate ribs. A directional guide member extends from the base plate and below the air duct and is configured to direct air flowing through the air duct rearwardly and toward the longitudinal center line of the engine.
In accordance with another aspect of the present ventilation arrangement, an outboard motor comprises a power head having an engine at least partially enclosed within a cowling, a driveshaft housing depending from the power head, and a propulsion unit driven by the engine. The engine has an air induction device positioned toward a front end of the engine and a protective cover positioned atop the engine. The cowling has an air inlet positioned at an upper rear end of the power head and an air guide positioned between the air inlet and the engine. The air guide has an air duct. The air duct and engine cover are arranged and configured to define a flow path of air from the air inlet through the duct and toward a rear end and a longitudinal center region of the engine. The engine air induction device is configured to draw air from the rear end of the engine across at least one side of the engine and into the induction device through an induction inlet.
In accordance with yet another aspect, the present ventilation arrangement includes an outboard motor comprising a power head having an engine substantially enclosed within a cowling, a driveshaft housing depending from the power head, and a propulsion device driven by the engine. The engine has an air intake device having at least one air intake inlet positioned at a front end of the engine. The cowling has an air inlet formed at an upper and rear portion of the cowling. An air guide member is positioned between the air inlet and the engine. An air duct is formed through the air guide member. The air duct defines an air flow path therethrough. An air directing member depends from the air guide member and extends across a forward portion of the air flow path downstream of the air duct. The directing member is configured to direct air flow rearwardly from the air duct.
In accordance with still another aspect of the present ventilation arrangement, an outboard motor is provided comprising a power head having an engine at least partially enclosed within a cowling, a driveshaft housing depending from the power head, a propulsion unit driven by the engine. The engine has an air induction device positioned toward a front end of the engine and a protective cover disposed over an upper surface of the engine. The cowling has an air inlet at an upper rear end of the power head and an air guide positioned between the air inlet and the engine Means are provided for directing air along a flow path through the air guide and between the air guide and the protective cover to a rear end of the engine, and further across at least one side of the engine to the air induction device.
In accordance with still a further aspect, the present ventilation arrangement includes an outboard motor comprising a power head having an engine at least partially enclosed within a cowling, a driveshaft housing depending from the power head, a propulsion unit driven by the engine. The engine has an air induction device having an induction inlet positioned at a front end of the engine and a protective cover atop the engine. The cowling has an air inlet at an upper and rear portion of the cowling. An air guide member is disposed between the air inlet and the engine. An air duct is formed through the air guide member. The air duct is configured to direct air flowing therethrough toward a rear of the engine. The cover has an upwarly-extending rib having a front portion disposed forwardly of the air duct and an aperture formed through the cover forwardly of the rib. The engine has a lubrication system comprising an oil tank and an oil filling tube. The filling tube extends through the aperture and has a filling port positioned above the cover and forwardly of the rib.
These and other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments, which refers to the attached figures. The invention is not limited, however, to the particular preferred embodiment that is disclosed.